Quantum ratchets and quantum heat pumps

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Abstract

Quantum ratchets are Brownian motors in which the quantum dynamics of particles induces qualitatively new behavior. We review a series of experiments in which asymmetric semiconductor devices of sub-micron dimensions are used to study quantum ratchets for electrons. In rocked quantum-dot ratchets electron-wave interference is used to create a non-linear voltage response, leading to a ratchet effect. The direction of the net ratchet current in this type of device can be sensitively controlled by changing one of the following experimental variables: a small external magnetic field, the amplitude of the rocking force, or the Fermi energy. We also describe a tunneling ratchet in which the current direction depends on temperature. In our discussion of the tunneling ratchet we distinguish between three contributions to the non-linear current-voltage characteristics that lead to the ratchet effect: thermal excitation over energy barriers, tunneling through barriers, and wave reflection from barriers. Finally, we discuss the operation of adiabatically rocked tunneling ratchets as heat pumps.

Detaljer

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Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Den kondenserade materiens fysik
Originalspråkengelska
Sidor (från-till)237-246
TidskriftApplied Physics A: Materials Science & Processing
Volym75
Utgåva nummer2
StatusPublished - 2002
PublikationskategoriForskning
Peer review utfördJa